The present invention relates to a guiding system for accessing a body cavity and directing the passage of devices therethrough into the cavity. Particularly, the present invention relates to a steerable catheter guiding system which directs the devices into the cavity in a desired orientation. In some embodiments, the present invention relates to endoluminally or transthoracically accessing an atrium of the heart to direct an interventional catheter toward a cardiac valve.
To access a target location within the human body from a remote location, a catheter is typically passed through one or more body lumens, such as through the vascular system, to the target location. When the vascular system is used, the catheter is inserted into an artery or vein percutaneously or through a relatively small incision in the patient's body. The catheter is then threaded through the patient's system of blood vessels to reach the desired target area. Often a pathway is created through the vasculature to the target location with the use of an introducer sheath. The sheath is slipped over a dilator or obturator which is advanced to the target location. The dilator or obturator is then removed and the sheath remains in place for use as a conduit for a variety of medical devices to access the target location. Such devices may include surgical instruments, fiber optic cables for visualization, lasers, electronic devices, or sensors capable of monitoring physiological parameters in situ to name a few. Although such access reduces the need for traditional invasive surgery, challenges arise related to control, manipulation, and positioning of instruments near the target location, particularly within a target body cavity.
Since cavities comprise open spaces, a device advanced to the cavity will typically protrude into the cavity at the angle in which it entered. If the target tissue is not within this pathway, the device will need to be steered toward the target tissue. If more than one device is used during a procedure, each device will need to be steered and repositioned when used. This increases the time and cost of the procedure and also the risk of misalignment.
For example, to gain access to the left atrium of the heart, the catheter and/or access sheath may be tracked from a puncture in the femoral vein, through the inferior vena cava, into the right atrium and through a puncture in the intra-atrial septum to the left atrium. When done for the purpose of mitral valve repair, this pathway may then be used to access the mitral valve which lies between the left atrium and the left ventricle. Since the mitral valve is located below the point of entry into the left atrium, devices which are inserted will need to be directed downward after entry, toward the mitral valve. In addition, devices used for applying interventional therapies to the mitral valve may require precise alignment with the valve commissures, leaflets, or coaptation line to perform the procedure. The devices may also be directed through the valve chordae or papillary muscles, for example, for interventional therapy to the mitral valve. When such procedures require the use of more than one instrument, each instrument would be dependent upon proper positioning in relation to the valve. This would require that positioning or steering mechanisms be built into each instrument and each instrument would be required to be properly positioned when introduced. This adds cost, complexity, and time to the overall procedure.
In other examples, the catheter and/or access sheath may also be tracked from a puncture in the femoral vein through the intra-atrial septum to the left atrium. This pathway may be used to access the left atrium for ablation of the atrium wall or ablation around the pulmonary veins. Such interventional therapies would require precise alignment with target areas for proper ablation placement. It may further be appreciated that alternative access routes may be desired to alternative body cavities. In any case, many of the same obstacles are encountered.
To overcome some of these challenges, pre-shaped access sheaths have been developed to direct instruments that are passed therethrough. For example, an access sheath having a pre-shaped curve at its distal end has been developed to both assist in negotiating twists and branches common in a patient's arterial or venous system and to maintain a shape once positioned within a target cavity. Since the pre-shaped curve is fixed into the access sheath at the time of manufacture, the radius, extent of the curvature and overall shape generally cannot be altered. Due to anatomical variations, extensive pre-surgical planning would be necessary to determine the correct curvature of the access sheath. Such tailoring would be prohibitively complex and a single predicted curvature would most likely still require additional repositioning once inside the body. Continuously replacing the single pre-shaped access catheter in hopes of obtaining the proper curvature would be expensive and time consuming, possibly placing the patient at additional risk.
Further, some steerable guide catheters and delivery catheters have been developed to more effectively navigate through the tortuous pathways of some body lumens, particularly the vascular system. However, navigation through such lumens typically only requires steering the catheter tip toward a particular branch at a bifurcation, a relatively simple maneuver. Such steerability, basically the ability to form a single curvature, is generally inadequate for accessing and directing the catheter toward a target in a cavity. In particular, when targeting the mitral valve within the cavity of the left atrium or left ventricle, many more variables are present, such as the type of approach, the variability of anatomy and the various targets associated with the mitral valve, such as various points on the leaflets, the commissures, the free edges, the chordae tendinae, etc. These variables increase the need for a steerable guide catheter that can provide a higher degree of articulation than a single curve catheter or a catheter which does not provide compound curves in an adjustable manner.
Additionally, some guiding catheters have steering mechanisms that operate using pullwires. Such pullwires are typically attached to the distal end of a catheter and, when placed under tension, operate to steer the catheter. However, the attachment of pullwires may fail when the pullwire is subjected to the forces required to steer or guide the catheter through the desired range of angles and curves. Pullwires may be soldered or welded in place, thereby strengthening the connection to the catheter, but this adds to manufacturing time and costs, and may introduce hazardous chemicals necessitating additional cleanup and processing before the device can be suitably and safely introduced into the body. Further still, a soldered or welded connection may result in a fairly rigid connection between the pullwire and the distal end of the catheter which may fail or break when placed under stress.
Furthermore, when multi-catheter systems are used, such as when one catheter is nested within another, maintaining the rotational relationship between the catheters requires additional mechanisms to prevent or limit the unwanted rotation of one catheter relative to another. Such multi-catheter systems can include a keyway component and a corresponding key. In order to provide the desired functionality, the key component must have sufficient mechanical hardness, and for this reason such catheters typically employ keys made from metal, such as stainless steel. However, the use of stainless steel or other metal necessitates machining of the component, and expensive process adding to the manufacturing cost of the resulting device. Additionally, adhesives are required in order to attach the stainless steel keys to a plastic catheter. The adhesive bond between the machined, stainless steel key and the plastic catheter may fail, resulting in loss of the intended keying function. Furthermore, the use of adhesives involves the use of additional chemicals and curing reaction products, and may require the expenditure of additional time and effort to prepare the catheter for safe introduction into the body.
For these reasons, it would be desirable to provide a guiding catheter system which is capable of being positioned within a target body cavity in a desired orientation. The system should have a steering mechanism capable of handling the forces required to curve and steer the catheter system in the desired position and through the desired range of angles necessary to achieve a desired orientation. Furthermore, the system should have a feature for preventing the unwanted rotation of one component relative to another, and these features should be capable of operating safely and effectively in a physiological environment. In addition, these features should be provided at low manufacturing time and cost. At least some of the embodiments disclosed below are directed toward these objectives.